Sprague-Dawley rats were addicted to alcohol using a liquid diet supplemented with ethanol by means of intubation. The rats were sacrificed at various times during and after ethanol treatment and their blood, spleen, and thymus examined for numbers of lymphocytes (blood, spleen, and thymus) and the ability of the lymphocytes to respond to non-specific T-cell mitogens. Animals treated with alcohol showed a decrease in lympocyte cell numbers in the peripheral blood, spleen and thymus and impaired ability to respond to non-specific T-cell mitogens (spleen cells only). Seven days after the end of ethanol treatment the rat lymphocytes appeared to have returned to control levels with regards to both cell number and function.